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DIOT reliability studies project
DIOT reliability studies project

Diot emc review meeting 1

Last edited by Volker Schramm
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01.06.2022

Participants: G. Daniluk, V. Schramm, D. Valuch

Notes

  • DI/OT Crate:
    • Better to use a metal version for the front panel ESD plug. It ensures good contact with the metal plate, and "pigtail" connection can be then avoided.
    • Info: The chosen starpoint is qualified for 50Hz
    • Starpoint of earthing cables could be moved to the side wall of the chassis. Today it's on a back panel, which complicates removal of that panel (however, in practice this panel is not meant to be removed once the crate is assembled).
    • Chassis structure looks good in terms of shielding -> if properly done the chassis can take the full shielding function which results in lower criticality for cables inside
    • For the ribbon cables inside the crate, the closer they are to the metal plate the better
    • BNC/Coax looks like it is isolated to the chassis which may lead to coupling of external disturbances through relays to inside the chassis -> Better to connect outer BNC to chassis
    • Regarding the usage of two backplanes (main + 2x power) no particularly negative effect is seen
    • Fan tray connector: shielded cable is recommended which is to be connected with the front panel. The shorter this cable is, less noise it will pick up.
    • In addition it would be beneficial to ensure that the cables (especially ribbon cables) won't touch the relay
    • If the fan tray is not connected in operation there is the possibility of coupling to the backplane through the ribbon cable -> therefore and in general it is advised to guide the cables inside close to the chassis (e.g. close to the metal plate that divides the front-panel space from the PSU space).
  • Profinet FMC:
    • For the 2 ethernet connectors it would be good to use a component with finger contact for a good connection to the front panel
    • Also a good connection of the front panel to a carrier front panel should be ensured to keep the path (connector->finger contacts->front panel->chassis) as short as possible - FMC EMC gaskets that are already used are good solution to that.
    • Good practice to verify the often fine gaps between the chassis polygon and other power/GND polygons. During tests often sparks are seen between one and another.
    • In general keep paths as short as possible and route currents away to the front panel as soon as possible
    • Electromagnetic gaskets to be used for the front panel connection
  • nanoFIP FMC:
    • Regarding the front panel and the SUB-D connector the same applies as for the Profinet FMC - SUB-D connector should be well touching an FMC front panel
  • Fan tray PCB:
    • SUB-D connector to be connected to the chassis
  • Radtol SB: (schematics not thoroughly pre-studied by Daniel)
    • Nothing particular detected on the design
  • Nonrad SB: (schematics not thoroughly pre-studied by Daniel)
    • No problem seen for the SFP cage which has contact fingers and usually a good connection
    • It should be made use of the existing mechanical anchors of the FMC mounting for a good chassis connection
    • The lower point of the FMC screw connection (next to the "DI/OT" writing) can be improved for a better connection with the chassis polygon
    • Very good that existing SI simulations have been performed
  • RaToPUS:
    • No particular review yet performed, but it has been good to collaborate closely with SY-EPC
    • Already performed individual EMC tests can or should be repeated with the ongoing new design